1. Field of the Invention
The present invention pertains to workflow process management. More particularly, this invention relates to a system and method for performing consistent and efficient workflow process execution in a workflow process management system.
2. Description of the Related Art
Workflow process re-engineering is the fundamental rethinking and re-implementation of workflow processes to achieve levels of quality, cost, throughput and service that have not been accomplished before. Workflow process management (WFPM) software, or more accurately, middleware, provides the enabling technologies for actually performing workflow process re-engineering. WFPM supports flexible solutions for the management of enterprise-wide operations, including workflow process control, automation and monitoring, resource allocation, authorization and authentication, task initialization and data exchange, and end-to-end communication and security.
WFPM can also be used to perform a wide range of tasks. For example, WFPM systems can manage existing non-automated legacy or work processes. As another example, WFPM systems can provide a method for defining and managing the flow of a work process or support the definition of resources and their attributes. In addition, they can assign resources to work, determine which steps will be executed next within a work process and when they will be executed and can ensure that the workflow process continues until proper termination. Moreover, they can notify resources about pending work, enforce administrative policies, such as access control and track execution and support user inquiries of status. Finally, they can provide history information in the form of an audit trail for completed workflow processes and collect statistical data for process and resource bottleneck analysis, flow optimization and automatic workload balancing.
Workflow process execution should be correct, efficient and flexible. In addition, workflow process execution should also be consistent. Workflow processes involve coordinated execution of activities performed by workflow resources (e.g., a person, a computer-based application, or an instrument). Workflow process execution involves accessing data items both internal and external to the workflow engine. Internal data items of each process execution is stored in a separate workflow process database that is managed by the workflow engine. External data items are stored in multiple action databases that are managed by external database management systems and are accessible by workflow activities, but not accessible by the workflow engine. The state of a workflow system is defined by the values of all data items involved in workflow process executions. A workflow system state is consistent if data items accessed and managed by different systems represent the same view of real world. For example, in a product design workflow system, the status of product design in the workflow process database managed by the workflow engine (for routing) should be consistent with that in the action database managed by external design system. A workflow process execution is consistent if each individual step sees a consistent workflow system state.
A prior solution for ensuring workflow process consistency is to adopt the concurrency control protocols used by database management systems. This solution executes each of the workflow activities as ACID transactions and employs concurrency control protocols such as two-phase locking to prevent undesired interaction among parallel activities. The approach ensures serializable execution of workflow activities.
One problem associated with this prior approach is that it requires sequential execution of parallel but conflicting workflow activities. While sequential execution of conflicting database operations (e.g., read and write) is acceptable, sequential execution of conflicting workflow activities is not acceptable, as they are generally long running.
In addition, serializability is not really needed in many workflow applications. This is the case not only because serializability is too costly to ensure, but also because the meaning of consistency in workflow is different from that in the database. In many workflow systems, a process execution is consistent if the data seen by the workflow engine is consistent with that seen by external workflow applications. Serializability is sufficient, but not necessary to ensure this level of consistency.
Thus, there is a need for a system and method for maintaining different levels of consistency and allowing concurrent execution of workflow activities.